Twin-fluke anchor



Filed Jan. 5, 1942 ufln R w WWW #12 3 E Q Q A. R m LL22 n fi a v f N: .1 2 3% r m w Patented Aug. 1, 1944 UNITED STATES PATENT OFFICE TWIN-{FLUKE ANCHOR Richard S. Danforth, Berkeley, Calif.

Application January 5, 1942, Serial No. 425,591

2 Claims.

In my Patent 2,249,546 of July 15, 1941, I have disclosed how a twin fluke type of anchor, as distinguished from a kedge type of anchor, can be successfully modified to adapt it to continued penetration under continued pull to the end that the anchor attains finally deep burial. As I have disclosed in my patent, the twin fluke type of anchor includes a shank and twin fluke arms, usually secured together as a unit, pivoted at one end of the shank to engage the ground together. That portion of the fluke structure joining the flukes together and providing the pivot mounting of the fiukes on the shank is usually termed the crown. This invention is concerned with the crown construction, particularly to certain improvements over that anchor shown in my aforementioned patent. These have to do with the relation of the various parts of the crown to the other portions of the anchor to the end that the iiukes rotate quickly to engage the ground as the anchor is drawn over the bottom so that the anchor, after the fiukes have engaged the ground, continues to do so until finally the anchor is deeply buried in the penetrable bottom. In addition, the invention is concerned with providing a simple crown structure wherein the shank is pivoted, the crown being so fashioned that earth or pebbles do not prevent the shank from pivoting freely, as is required, in the crown structure.

The invention includes other objects and features of advantage, some of which, together with the foregoing, will appear hereinafter wherein the preferred form of anchor of this invention is disclosed.

In the drawing accompanying and forming a part hereof,

Figure 1 is a side elevation of a preferred form of my improved anchor, with the flukes in final operative position;

Figure 2 is a plan view of the same form, as it would appear when lying on a flat surface;

1 Figure 3 is a section through the crown I2 of the same form, as on the line 3-3 of Figure 2;

Figure 4 is a cross section through the crown l2, as on the line 4-4 of Figure 2.

The anchor shown in Figures 1 to 4 consists of three separable parts: shank II], a twin-fluke unit comprising the crown I2, fluke arms Il--l| and flukes I l-l4, and a stock I3 which passes through the crown and the after end of the shank to act as a pivot for the fluke unit. (Throughout this description and in the claims, the end of the anchor to which the cable is attached will be refluke unit is pivoted will be referred to as the after end.) The forward end of the shank is provided with a shackle l6 for the attachment of a chain or cable.

The shank is preferably tapered longitudinally, as is illustrated in Figure 1, this form giving 'the greatest strength at the after end where the maximum bending stresses occur. The stock, which is preferably tapered as shown, passes through holes bored or cored in the after end of the shank and the cheeks 25 of the crown. The cheeks are connected by webs 21 which can be relieved centrally as at 28 to reduce the resistance area as much as is feasible. In the form of anchor shown, the crown is cored out as at 29 from the front to the rear thereof. This provides a receptacle for the after end of the shank. The forward looking internal faces l5 are bevelled at the angle which it is desired that the flukes should assume in operating position. The cored out portion 29 provides an opening through the crown through which any mud or sand can pass.

The fluke arms I IH and the fiukes I4l4 are integral with the crown and with each other and may suitably be formed as a single steel casting. The fluke arms taper forwardly and form a rib 30 along the inner edge of each fluke. The fiukes themselves are relatively thin plates; for example the fiukes in the smaller size anchors, those weighing less than pounds, range between thick adjacent the rib and T35" adjacent the outer edges, for a 30 pound anchor and up to 1% and T 6 respectively for a 150 pound anchor. These edges are bevelled as at 24 to a relatively sharp immediate edge and the fluke should be brought to a sharp point as shown. This combination of thin plate fluke and reinforcing rib, in the triangular form shown, has a high relation of strength to weight and a very desirable bottom penetrating characteristic.

The bores through the after end of the shank and the cheeks of the crown are provided with grooves 2! so placed that, with th shank in the proper position, they form a continuous channel. The stock is provided with two lugs 22 and 22', the former being of such dimensions as to pass through the channel, the latter being considerably larger. The stock being passed through the bores in the assembled shank and crown, the smaller lug passes through channel 2| to the opposite face of the crown, after which a slight revolution of the stock takes the lug out of register with the channel and prevents its return. The stock is held against return rotation in any convenient manner, as by means of a cotter pin 26 passed through the stock and between lugs 30 on the crown to hold the stock against rotation. In this manner of assembling the shock occasioned upon the anchor falling on one end of the stock is taken by the lugs and no stress is thrown on the cotter pin.

The structure of the crown is important for upon it depends the rapidity with which the flukes engage and dig into the bottom. Further, if the crown is not properly formed the crown itself may dig into the ground prematurely and thus eliminate the lift of the after end of the anchor and by which the points of the flukes are brought into angular contact with the ground to initiate engagement. In the form of anchor shown, the fiat smooth face 3| on each side of the shank is inclined toward the axis of the fluke and, when dragged forwardly, rides up even on soft ground to lift the after end of the anchor, while offering relatively little resistance to burial. The faces 3| are made up in part by a flange or rib 23 on each side of the crown to provide sufficient lift area which can be increased to any desired width without increasing the weight of the anchor materially.

It is wholly essential that the faces arranged to produce lift be sloped upwardly opposite to the direction of dragging. If the angle of the faces is too steep, they act as grips and prevent burial. They are preferably sloped at about 35 and between 25 and 45 is a good range. Further, it is also desirable that they be centrally located, i. e., on or close to the longitudinal axis of the shank. If such faces be spaced any material distance from this axis, even if the disposition is completely symmetrical, they are almost certain to set up a tendency toward rotation under certain conditions. On the other hand, any portions of these faces lying directly under or back of the shank are liable to be rendered ineffective by the trenching effect of the forward end of the shank, lift of the after end being required solely in advance of engagement and therefore at a time when there is no resistance to cause the forward end of the shank to lift away from the ground. It is for this rea son that the crown is relieved at 28. Consequently, the faces producing lift should be symmetrically located as regards the shank axis and as close thereto as is consistent with bearing on ground lying on each side of the shank.

Rotation of the flukes is only a portion of the problem of ensuring quick engagement of the flukes. For example, in soft mud the anchor can drag along with the shank of the anchor at an angle to the bottom with the flukes lying above the shank and the crown end partially buried in the mud. It is necessary to lift the crown end of the anchor to the surface and cause the flukes to rotate to the other side of the shanks and engage. By continuing the faces 23 rearwardly, as will be explained, this can be achieved; face portions 35 continue faces 23 but are substantially parallel to the plane of the fluke faces, or slope upwardly r downwardly a little, to provide lift surfaces effective at the crown end without increasing substantially the resistance area of the anchor as this is defined in my Patent 2,249,546 of July 15, 1941.

The crown construction is applicable to twin fluke anchors wherein more than 65% of the fluke area is forward of the pivot, as disclosed in my aforesaid patent, as well as to those wherein the fluke area is approximately balanced as in my application Serial No. 401,323 filed July 7, 1941, now Patent 2,282,566.

A very useful addition to an anchor of this type is the guard indicated at 32 in Figures 1 and 2. This is essentially a substantially flat plate fastened in any manner at the after end of the crown and of such area as to cover the opening 29. In the form of anchor shown in the drawing, the plate is joined at the rear of the crown to each side thereof but spaced from the crown to permit material to issue from passage 29. In this case, the anchor is relieved at 36 to permit free issue of material. The plate prevents material from entering if the anchor should be dropped on the bottom with the rear of the crown down. The possibility of the fluke unit becoming jammed by entrance of a pebble or other like element as a piece of wood is thus avoided. The ring 33 on the rear of the plate is also useful at times in breaking the anchor out if "it should become fouled as on a mooring chain; a float line can be secured to this end of an anchor to permit a direct pull thereon.

While I have heretofore employed the term stock as applied to element l3, and have shown this as a separatable element, it shouldbe understood that this element can be integral with the fluke structure as in Figures 11, 12 and 13 of my patent and as in my aforementioned application. Whether it is a separate element or an integral part the term stock is used herein and in the claims as applied to the means extending laterally of the shank and effective to prevent the anchor from riding on its side, to position the anchor so both flukes initially engage the ground, and to stabilize the anchor and prevent rotation.

I claim:

1, An anchor comprising a stock; a shank; a pair of flukes extending generally in a common plane and pivoted at one end of said'shank; and a crown joining said flukes together and having ground-engaging portions, each of said portions including a portion sloping rearwardly away from the plane of the flukes at an angle to the plane of the flukes of between 25 and 45 and having a portion extending rearwardly from said firstmentioned portion to provide a substantially flat face approximately parallel to the plane of the flukes and spaced from the plane of the flukes and effective, when the anchor i drawn over bottom, to raise the crown end of the anchor and so rotate the flukes on their pivot without greatly increasing the resistance to burial of the anchor.

2. An anchor of the class described comprising a shank having a forward and an after end, a stock, a pair of flukes, a crown joining said flukes adjacent their after ends and having an opening in said crown, said shank being pivoted at its after end in said crown, said crown having ground engaging portions thereon having an initial portion sloping rearwardly and outwardly from the flukes on each side thereof at an angle thereto of between 25 and 45 to a terminal portion extending rearwardly from said initial portion to provide a substantially flat face approximately parallel to the plane of the flukes and terminating above the fluke faces to slide along the ground and rotate the flukes when the anchor is on the ground, and a plate extending in a spaced relation across said opening at the rear of said crown and spaced therefrom to provide a passageway from said opening, said plate terminating short of the extreme ground engaging crown portions on each side thereof.

RICHARD S. DANFORTH. 

